This is not a BC break IMO. If you have the fullstack 2.2, you cannot use TwigBundle 2.5 anyway (as TwigBundle is part of the fullstack).
And if you use them standalone, composer will forbid you to upgrade to TwigBundle 2.5 without upgrading Twig-bridge as well, but this is part of the dependency resolution. If you try to do the job of composer manually, you are asking for pain anyway.